When I try to install Wine, PlayonLinux, and some other programs, I get the following message:

At the terminal:

The following packages have unmet dependencies:
wine : Depends: wine1.5 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

At the software center:

Package dependencies cannot be resolved
This error could be caused by required additional software packages which are missing or not installable. Furthermore there could be a conflict between software packages which are not allowed to be installed at the same time.

I already tried installing them with "aptitude" and failed.

I am running Ubuntu 12.10

Please help! I've had this problem for a while now and don't know what to do!

IF THI NO WORK, TRY THIS:
I suggest you to do these: (most of the cases, it works)

Install aptitude with sudo apt-get install aptitude command

Try to install the package you are willing to install with command like

sudo aptitude install
Aptitude will show you the error and present you a possible (best) solution. You will be asked to choose from 3 options with a message like

Accept this solution? [Y/n/q/?]
If you see that your desired package is not listed in the (will be) installed list, simply press n to let aptitude give you the next best solution. After several trial, (if you are lucky) you will see that your desired packages are in installable list and the packages causing the dependency problems will be showing in downgrade list. In this stage Press Y to accept the solution. The packages will be downgraded to satisfy to installation request.

I'm sorry that, I can't give you a demo run of aptitude like this, but you can check this page to see some of it's action.

If, while doing this, you can identify the broken package, this command will very forcefully remove it: